The present invention relates to a clamp for fixing a seat post to a seat tube of a bicycle.
As is known, the saddle of a bicycle is carried by a tubular element (seat post) which is slidably inserted inside a vertical tube, namely, the seat tube, of the bicycle frame. The seat tube carrying the seat post is provided with a through slit made in an end portion of the tube, which bestows on said end portion characteristics of elastic deformability in the radial direction. The end portion of the seat tube is tightened against the outer surface of the seat post by means of a clamp having a slit which is set aligned to the slit of the seat tube and which is radially compressed by means of a screw which brings two elastically deformable branches of the clamp up to one another. For aesthetic reasons, the tightening screw is set on the side of the seat tube that faces the rear part of the bicycle.
Recently there have been introduced on the market seat posts made of carbon fiber, which consist of a fiber fabric embedded in a matrix of plastic material. A seat post made of carbon fiber makes it possible to obtain a reduction in weight as compared to a component having the same characteristics which is made, for instance, of an aluminium alloy or similar light alloys.
The traditional solution described previously for fixing the seat post to the seat tube presents a serious drawback in the case where the seat post is made of a carbon-fiber fabric embedded in a matrix of plastic material. The present applicant has found that, when a clamp of a traditional type is tightened around the end portion of the seat tube, the two internal edges defined by the through slit of the seat tube are deformed inwards and tend to cut into the outer surface of the seat post. These incisions form points of initiation of failure, which in certain cases may lead to failure of the seat post.
The purpose of the present invention is to overcome the aforesaid drawback by providing a simple and effective solution that does not entail the need to modify the seat tubes with respect to current solutions and that makes it possible to keep the tightening screw set in the rear part of the seat tube.
According to the present invention, the above purpose is achieved by a clamp having the characteristics specified in claim 1.